As a tire noise, a road noise is known, which is generated in a frequency range between about 50 and 400 Hz. This arises principally due to columnar resonance (cavity resonance) occurred in the tire cavity. Thereupon, to reduce such a road noise, the following Patent Document 1 proposes a technique of applying a noise reducer made of sponge material to a tire cavity surface, for example. This noise reducer is formed in a jointless ring shape and is mounted inside the tire cavity in a compressed state.
Patent Document 1: Japanese Unexamined Patent Application
Publication No. 2005-254924.